1. Field of the Invention
This invention relates to a flotation barrier or boom, and, more particularly, to an improved contamination control barrier or boom which can be used to contain an immiscible contaminant floating on a body of higher density liquid.
2. Description of the Prior Art
The increased contamination of bodies of water such as rivers, harbors, ponds, lakes, and oceans, by oil spills, chemical spills, and other contaminants, has created a growing need for effective containment and recovery means.
The problem is particularly acute in the case of oil spills. As the supply of oil becomes more scarce, exploration and production activities are increasingly being conducted offshore. This increases the risk of offshore oil leaks, as from blowouts or pipe failure. In addition, seagoing tankers with storage capacities of millions of gallons are employed in transporting crude oil and refined petroleum products.
Hydrocarbon liquids constitute a dangerous source of pollution, since they have densities lower than that of water and will float on and spread over wide areas of water. Apart from being a fire hazard in the shipping lanes, these floating liquids can seriously pollute nearby land areas. The devastating environmental and legal implications of liquid hydrocarbon spills on a body of water are well known.
The effectiveness of recovery of an oil spill is maximized, and the damage to the environment minimized, by confining the contaminant to as small an area as possible. This requires that the containment operations be implemented as soon as possible after the occurrence of the spill.
Methods for removing hydrocarbon liquids and restoring the quality of the water to desired characteristics include the use of chemical additives to cause a change in the characteristics of the oil; the use of various materials to absorb the oil from the water; and the use of confining devices and recovery means to prevent spread of the oil and remove the oil from the surface of the water.
Floating barriers, known generally as oil booms, have been found to have great utility in containing and controlling oil slicks and other water carried pollutants on bodies of water. The barriers usually contain flotation elements having a liquid impervious skirt which, when deployed, provide means for containing the pollutant or preventing the pollutant from spreading into uncontaminated areas.
A large variety of barriers or booms are utilized to separate the contaminated area from adjacent uncontaminated areas. A common characteristic of oil spill booms is that they are designed to float in the water with part of their structure above and part of their structure below the water level. The portion above the water level serves to contain the floating oil and prevent splashover of the oil. The portion below the water surface serves to contain the oil below the surface and prevents oil from escaping under the barrier.
Typical of such oil containment booms are those described in U.S. Pat. Nos. 3,476,246 and 4,062,191. Both patents disclose a boom comprising a series of inflatable air tubes to provide buoyancy and a weighted skirt to serve as an underwater barrier and to preserve the orientation of the boom. The devices are fairly complicated and have rigid components. This renders them expensive to manufacture and cumbersome to store and deploy.
Another type of boom, disclosed in U.S. Pat. No. Re. 28,966, obviates the need for using a weighted skirt. This boom comprises a structure having a buoyant upper section and a water absorbing lower section. While eliminating the need for weighted skirts, this boom still suffers from being rigid and complex, and thus expensive to manufacture and cumbersome to store and deploy.
Yet another type of oil boom is disclosed in British Pat. Nos. 1,188,156 and 1,383,315 and U.S. Pat. Nos. 4,140,424, 4,112,689, 4,207,191, and 4,310,415. All disclose variations or improvements of an oil boom comprising two chambers made of a flexible material. Prior to use, the barriers can be rolled up and packed into a relatively small space for transport and storage. Upon deployment, one chamber is inflated with water while the other is inflated with air and each chamber takes on a substantially cylindrical shape. The two cylindrical chambers, being connected to each other at a point on their circumferences so as to form a figure eight cross section, then forms a barrier with the water chamber being under the water line and the air chamber floating above the water line.
While this type of boom is inexpensive to manufacture and can be easily stored and easily and rapidly deployed, it suffers from being limited to use in calm conditions. This disadvantage comes about from the fact that the figure eight configuration of the air and water chambers lacks the orientational stability required to withstand wave and wind action while maintaining the effectiveness of the barrier. British Pat. No. 1,188,156 discloses that the barrier behaves particularly well when the underwater portion has neutral buoyancy. However, a neutrally buoyant water chamber will not, when perturbed, normally orient itself vertically downward. Rather, the chamber will shift from side to side in response to even moderate wave or current action. The result will be an air chamber which stays above the water level but a water chamber which easily shifts position under the water.